So soon, I will be running an eight player game for my family, some of which will be playing by Skype. My sister is playing a sorcerer who is also a noble lady. As she felt the two Sorcerous Origins were too undignified, she asked me to create one for her. Here is the Spellborn:

Spellborn

Your innate magic comes from a spell cast on or by your mother while you were in the womb. You absorbed some of the magical energy, and it gives power over magic itself. Your parents might have been victims of an evil warlock, or maybe powerful wizards always trying new spells.

Magical Affinity

At 1st level, choose a school of magic. This is the school of the spell that resulted in your extraordinary birth. For each spell in that school on your spell list, choose one: Increase range by twenty feet; Move damage dice up one; Take advantage on attack rolls or other rolls; Increase duration by one hour.

Spell Resistance

Your body is partially protected against spell effects. You have advantage on saving throws against spell effects, and spell attack rolls against you have disadvantage.

Power Well

You are increasingly connected to the magic all around you. At 6th level, choose two more spells from your chosen school at 1st or 2nd level. At 14th level choose another, at 5th or 6th level. At 18th level choose another at any level spell.

Spell-like Form

At 14th level, your body has become similar to the frail wisps of magic you wizards store in artifacts. Add one to your Dexterity. Whenever someone casts counterspell within 60 ft of you, the magic within you reacts, causing you 4d8 of damage.

Natural Glamour

At 18th level, you have mastered the magic that makes you entirely. You can cast illusions on yourself indefinetely, making yourself look however you wish. When you use this, other sentient beings have to make a DC 20+Your Charisma modifier Wisdom check to realize it is false. Mindless beings automatically accept it as true, even if they touch you, as you warp reality.

If you wouldn't mind, please tell me what you think!

Are you ever going to do stuff over 20th level?

The 14th-level feature is a severe disadvantage.  Picture this. . .

The party is about to be subjected to a powerful spell, such as cone of cold. None of the spellcasters have counterspell prepared, to avoid hurting the sorcerer.  No one can cast counterspell to stop it, so everyone suffers the effect of the spell; in this case, 8d8 cold damage, Con save for half.  Or, if someone does have counterspell prepared, the enemy spellcaster counterspells the counterspell, and the sorcerer takes an extra 8d8 typeless damage.  

I added that because I thought it was a cool idea for a half-spell being to be affected by counterspell... should I tone it down? I do want to keep the original idea.

I love the flavor but the 1st level abilities are way over the top. Magic resistance at 1st level?

And Matthias is correct. I don't understand the 14th level feature. Plus one dex to take 4d8 from a counterspell? One extra point of dex may not even increase the ability modifier for the character!

One suggestion...maybe some of these abilities should require sorcery points? 

Oh! Good idea! Thanks for the feedback... You think it would work if I took out Spell Resistance altogether and just left the other 1st level effect?

Quote from Serifey >>

I added that because I thought it was a cool idea for a half-spell being to be affected by counterspell... should I tone it down? I do want to keep the original idea.

Hmmmm, good ideas! I think I like the first one best.

Have you been able to create this as homebrew content in dndbeyond?

Still learning my way around the tool, and looking for a way to create a homebrew Sorcerous Origin for our resident Tiefling to port the character over to dndbeyond.

Magical Affinity

At 1st level, choose a school of magic. This is the school of the spell that resulted in your extraordinary birth. For each spell in that school on your spell list, choose one: Increase range by twenty feet; Move damage dice up one; Take advantage on attack rolls or other rolls; Increase duration by one hour.

Increasing range is OK but it does infringe on the grounds of metamagic Distant Spell especially concerning touch attacks. Increasing the damage dice for any spell is incredibly overpowered - for example a Fireball of 8d6 becomes 8d8 for a level 3 spell. Combined with metamagic like Empowered and this is rather extreme and can instantly make you the most damaging spellcaster in all of D&D. So, nope. Likewise advantage on all attack rolls at 1st level, no risk? Level 20 features don't grant this, it's extreme and you even say "other rolls" so basically your level 1 character is more successful at everything that can be possibly done than any other Level 20 and beyond beings in all of D&D. Again, nope. Increasing duration by an hour is also way overpowered. For example you could use Absorb Elements as a reaction to absorb damage and now suddenly you can do an extra 1d6 element damage for the next 100 combat rounds, no concentration required. Let's consider Color Spray which affects multiple creatures and blinds for a turn, with your class feature those creatures are now blinded for an hour, no concentration required and no saving throws to avoid - just like that you've granted advantage on all attacks by anyone against them and disadvantage on all attacks by them for an hour - you've basically won the fight by casting one 1st level spell. An hour's worth of Feather Fall and you are just like that immune to all falling (because you could fall from space to the ground in far less than an hour!). And then Shield - with one casting, which is a reaction, you are, without any concentration, up +5 to your AC for the next 100 combat rounds, which is +8 when combined with Mage Armor.

Now consider later you can choose Extended Spell metamagic to double duration... Yikes.

Your 1st level feature is more powerful than several Level 20 features combined and then some.

How about sticking to something like choosing a 1st level spell of the chosen school which you get to add to your known list without counting against maximum known spells and you get to use it once per day (long rest) without spending a spell slot? I'd add that "Unlike your other spells the ones selected through this feature cannot be changed when you advance in class levels. "

Alternatively consider granting a free cantrip of the chosen school.

Spell Resistance

Your body is partially protected against spell effects. You have advantage on saving throws against spell effects, and spell attack rolls against you have disadvantage.

Yeah way too overpowered. Spell Resistance like this is typically mid-late level stuff. I'd consider maybe you have +2 bonus to saving throws/AC versus magic. Or keep as it is but limit it to using your reaction and only once per Long Rest.

Power Well

You are increasingly connected to the magic all around you. At 6th level, choose two more spells from your chosen school at 1st or 2nd level. At 14th level choose another, at 5th or 6th level. At 18th level choose another at any level spell.

This is good but I would say: At 6th level you learn 2 more spells of 2nd level or lower from the chosen school of magic. These spells do not count against your maximum number of known spells. You can choose an additional spell of 5th level or lower from your chosen school of magic when you reach 14th level and another spell of 8th level or lower from your chosen school when you reach 18th level. Unlike your other spells the ones selected through this feature cannot be changed when you advance in class levels.

This keeps the additional spells more balanced and isn't effectively making you a wizard and prohibits being able to choose a free 9th level spell to know because that's a tad overpowered. Don't forget Sorcerers can change their known spells when they increase in levels so you have to be careful when granting free spells to know.

Spell-like Form

At 14th level, your body has become similar to the frail wisps of magic you wizards store in artifacts. Add one to your Dexterity. Whenever someone casts counterspell within 60 ft of you, the magic within you reacts, causing you 4d8 of damage.

This doesn't make sense. The idea of class features is to grant benefits to characters. I see no purpose in causing hinderances and vulnerabilties without a suitable payoff which you don't provide (+1 to dex? Even +2 is not that useful - they can already get ability score increases and improve their AC with spells). It also doesn't make sense to become more vulnerable to magic when you started with resistance to magic. What incentive would a person have to choose this class which suddenly nerfs them at level 14, where enemies get stronger and use more magic against you?

To go with a 'Spell Form' route I would consider that they can enter a new form for a cost of Sorcery Points (around 5 or 6) for about a minute. The form would grant benefits depending on their chosen school. For example Evocation may mean a close damaging area of a chosen element type and being able to add Charisma onto damage of any Evocation spell you cast. Abjuration could mean gaining a ward to absorb damage similar to a wizard's Arcane Ward feature. Something like that. I'm not going through all the schools but this would make more sense and keep it more in line with other sorcerous origins.

Natural Glamour

At 18th level, you have mastered the magic that makes you entirely. You can cast illusions on yourself indefinetely, making yourself look however you wish. When you use this, other sentient beings have to make a DC 20+Your Charisma modifier Wisdom check to realize it is false. Mindless beings automatically accept it as true, even if they touch you, as you warp reality.

This makes no sense either. Why does having a connection to a school of magic, like Evocation, suddenly make you super-illusionist? DC 20 + Cha ? Heck no! You get that by this level you should have a +5 cha or higher. DC 25? Really? You realise DC 30 is "almost impossible", right? And Wisdom check? Nope.

If going illusion route, for reasons I cannot fathom with this origin, try just "You learn the Disguise Self spell and this does not count towards your maximum known spells. If you already know this spell you may learn a different 1st Level spell instead. You can cast Disguise Self at-will without requiring spell-slots.

Personally, I would keep with the school route. "When you reach 18th level you may select a 1st level spell of your chosen school that you know. You may cast this spell at-will without needing material components or expending any spell slots."

I like the idea/theme of your origin but it is extremely overpowered compared to other origins and some features, as mentioned, do not make sense with the theme or the idea of classes in general.

Quote from Lady_Kalla >>

Are you ever going to do stuff over 20th level?

Quote from Scalefist >>

Have you been able to create this as homebrew content in dndbeyond?

Still learning my way around the tool, and looking for a way to create a homebrew Sorcerous Origin for our resident Tiefling to port the character over to dndbeyond.

Wow! Thanks for such detailed advice! I am going to be rewriting/editing this soon, and I'll definitely take at least half of this advice. One question: For your idea for the 14th level ability, what do you think necromancy's ability would be? 

Quote from Serifey >>

Wow! Thanks for such detailed advice! I am going to be rewriting/editing this soon, and I'll definitely take at least half of this advice. One question: For your idea for the 14th level ability, what do you think necromancy's ability would be?